Beam registration system



Jan. 12, 1960 A. LIEBSCHER 2,921,117

BEAM REGISTRATION SYSTEM Original Filed Jan. 27, 1948 United StatesPatent() 2,921,117 BEAM REGISTRATION SYSTEM Arthur Liebscher,Jenkintown, Pa., assignor to Radio Corporation of America, a corporationof Delaware 28 Claims. (Cl. 178-5.4)

This invention relates to color television and more particularly to thepickup, transmission and reproduction` of images in'substantially theirnatural color.

This application is a continuation of my application, Serial No. 4,660,filed January 27, 1948, and entitled Color Television System.

Images in substantially their natural color may be transmitted overelectrical circuits by analyzing the light from the object into not onlyits image elements, but by also analyzing the light of the object intoselected primary or component colors and deriving therefrom signaltrains of impulses representative of each of the selected componentlcolors. The image in substantially its natural color may then bereproduced at a remote location by appropriate reconstruction from thecomponent color signal trains.

The transmission and reproduction of color images may be accomplished byeither of two fundamental systems of multiple image transmission whichhave become 4widely .known as the` simultaneous and the sequentialsystems of color image transmission.

The simultaneous system transmits all component color signal trainssimultaneously through three separate signal channels.

The sequential system transmitsat any one time only one component colorsignal train, and transmits in predetermined sequence a portion of eachof the selected component color signal trains.

The device employed for converting light from an object into a signaltrain is commonly known as a television camera. In the transmission ofimages by the sequential method, the camera may have a single imagepickup tube, such as, rfor example, the so-called image orthicon, whichis exposed in succession to images giving color separation correspondingto the various selected component colors. During the period that thecamera tube is exposed to each color component image, the mosaic isconcurrently scanned to enable the transmission of signals representingthe corresponding color separation image.

Image pickup tubes may take various forms. An irnage orthicon camera isshown and described in an article entitled Image Orthicon Camera by R.D. Kell and G. C. Sziklai in the RCA Review for March 1946.

In the conventional sequential multicolor television receiver, akinescope or other image producing tube is employed to recreate a blackand white image likeness which is viewed or projected through a colorlter of the selected component color corresponding to the desiredcomponent color instantaneously being represented. The process is thenrepeated for the neXt selected vcolor component, and so on. A typicalsequential color television system is shown and described in anarticleentitled An Experimental Color Television System, beginning on page 141of the RCA Review for lune 1946.

Although color images have been successfully reproduced by theafore-mentioned sequential method, there are certain fundamentaldifficulties involved `which tend to reduce the entertainment value ofthe sequential sysf 'ice tern. Typical difficulties involved includecolor action fringes, resulting from movement between individualcomponent color scannings, and inadequacy of illumination, which results`from the required division of available light for the reproduction in asequential manner of the individual selected color component images.

The fundamental difficulties, particularly the color action fringes,referred to above for the sequential method are eliminated if the rateof change between the selected component colors is made rapid enough toovercome any indication of movement between the different selected colorrepresentations.

If, for example, an elemental sequential rate is employed, that is, ifeach image element is divided into three selected component colors, andfor each elemental area of the image there are transmitted sequentiallythree different color representations, each of whose amplitude or energydepends upon the selected color components of the image element, nodifficulty will be experienced with color action fringes.

It becomes apparent, however, that such an arrangement would require notonly accurate synchronism in the scanning raster, but it would requirealso proper color phasing by such means as'maintaining an accuratesynchronism or speed control in each traverse of the scanning element inorder that the corresponding `color representation at both thetransmitter and receiver would be scanned in perfect synchronism.

According to this invention, an improved method and arrangement isprovided whereby color television signals are transmitted in anelemental sequential arrangement and there is employed a sweep speedsynchronizing pulse having a repetition rate elemental frequencies. Inone form of the'invention, the sweep speed synchronizing pulse isdeveloped in the transmitter by employment of a strip type filterinvolving not only the red, blue and green components, but also anultraviolet lilter for producing a uniform signal impulse upon scanning.In the receiver, the sweep speed synchronizing pulse is compared with apulse developed by the scanning operation in the receiving tube. The twosweep speed pulses are compared tocontrol the sweep speed in the imagereproducing tube, whereby to effect the desired color phaslng.

A primary object of this invention is therefore to provide an improvedcolor television system.

Another object of this invention isto eliminate color action fringes insequential color television systems.

Still another object of this invention is to eliminate registrationproblems in color television systems.

Still `another object of this invention is to maintain accurate sweepspeed synchronism at the receiving station with the sweep speed ofdeflection at the transmitting stations.

Other and 4incidental objects of the invention will be. apparent tothose skilled in the art from a reading of the Ifollowing specificationand an inspection of the accompanying drawing in which:

Figure 1 shows in block diagram on form of this invention as it may beemployed at the transmitting station;

Figure 2 illustrates a greatly enlarged section of an electron beamscanning target; and

Figure 3 shows by block and vcircuit diagram one form of this inventionsuitable for employment at the receiving stations.

Turning now in more detail to Figure 1, there is shown a transmittingtube 1, which, in general, may take any of the well-known forms. Asshown, it takes the form of the well-known image orthicon type tubewhich is well shown and described in an article entitled The ImageOrthicon, A Sensitive Television Image Pickup Tube,

published in the Proceedings of the Institute of Radio Engineers forJuly 1946.

Although details regarding circuit arrangements for maintaining`deflection and focus of the scanning beam are not shown or described indetail, it is believed that various arrangements for accomplishingdeliection and focus are well-known in the art and need no detaileddescription here.

The transmitting tube 1 does, however, have an important difference fromthat shown and described in the published art. This difference, inaccordance with this invention, may be found in the structure of thetarget 3, which consists, in one form, of a plurality of similar groupsof strip-like sections, each strip-like section of a group being limitedin its representation to one different selected color component of acorrespondingimage sectional area or a reference signalimpulse formingarea,

A brief reference to Figure 2 will more clearly illustrate the form ofthe electron beam target 3 of Figure l.

In Figure 2, the photo-emissive material 5 is located on the back of thesimilar groups of strip-like sections involving, as illustrated, filterelements of red, blue and green, together with a filter element ofultraviolet.

Although the target section shown in Figure 2 includes filter elements,the target structure may include, for transmitting purposes, a colorsensitive photo mosaic surface. Another alternate arrangement may beemployed when target 3 of Figure l is used in a transmitter tube withoutan image section. It will be seen that in the form of the inventionshown in Figure 1, the target 3 involving the strip-like sections is notthe target upon which the electron scanning beam of the tube 1 impinges.Target 7 of tube 1 is impacted by the electron beam of tube 1. Inaccordance with a well-known theory of the image tube, the target 3produces an electron image which is electrically focussed on target 7.

Turning again to Figure 2, it follows that if the light approaches fromthe front, the photosensitive area 5 will have an electricalrepresentation developed thereon, de-

pending upon the color of the incident light and the color of theassociated filter section. If, for example, a red light is projectedupon the target 3 from the object 9 of Figure l, only that portion ofthe photosensitive element 5 behind the red filter sections will beactivated. Therefore, the signal developed by the scanning operation oftube 1 will` provide signal impulses only at the time the electronscanning beam scans the area of target 7 corresponding to the areabehind each of the red filter sections of target 3 of tube 1. This istrue for each of the selected component colors.

If, however, a lamp 11 is provided with an ultraviolet lter 13 in orderto provide a constant illumination of ultraviolet light on electrode 3,a series of substantially uniform pulses will be developed as thescanning beam traverses target 7. A pulse will be formed each time thescanning beam traverses a section of target 7 which corresponds to thesection of electrode 3 which is immediately behind the ultravioletfilter sections.

It will therefore be seen that if no light is projected on electrode 3from object 9, and if lamp 11 illuminates electrode 3 with anultraviolet light, a series of impulses will be developed in transmittertube 1 whose rate of recurrence is equal to the rate of deflection ofthe 4scanning beam across the ultraviolet filter sections.

If, for example, the filter sections illustrated in Figure 2 are made ofa size such that each group of filter sections involving a red, blue,green and ultraviolet section .is made to correspond with an imageelement size, the

signal impulses generated by the scanning of the ultraviolet filtersections will correspond to an elemental frequency.

If this beam traverse speed control signal developed by the scanningoperation of transmitting tube 1 is transmitted, together with videosignals developed as a result of the light; projected onelectrodcSbycolored object 9,

.4 the combination may be employed at the receiver for not only thereproduction of images, but also the receiving system scanning traversespeed control.

In the form of the invention shown in Figure l, the signal developed bythe transmitter tube 1 is amplified in video amplifier 15 andcaused tomodulate the television transmitter 17 by modulator 19.

Modulator 19 also receives a deflection synchronizing signal from syncgenerator 21. The deection synchronizing signal o-f synchronizinggenerator 21 is also employed in the well-known manner for the controlof horizontal deflection and vertical deflection of the transmitter tube1 through horizontal deflection control 23 and vertical deflectioncontrol 25.

Turning now to Figure 3, there is illustrated a television receiver 27,which may take any of the well-known forms capable of the reception of arelatively wide signal pass band.

Video amplier 29 provides the control electrode 3l of image reproducingtube 33 with potential variations to vcontrol the intensity of thedeveloped scanning beam in accordance with the video signal.

The image reproducing tube 33 may take, in general, any of theWell-known forms, such as, for example, the popular kinescope, which iswell described in the published art.

There is, however, an important difference in the kinescope 33 modifiedto operate in accordance with this invention. The difference residesinthe screen 35 which,

in .the form of the invention shown, takes the form of adjacentlypositioned and similar groups of strip-like sections, wherein eachstrip-like section of the group is limited in its effective reproductionto one different selected color component of the corresponding imagesectional area. The enlarged View of the multiple target may take theform of that shown in Figure 2, wherein the red, blue, green andultraviolet filter sections are applied to the light producing element,which might take the form of a white phosphor 5.

The beam generation yand deflection involved in kinescope 33 follows thewell-known forms of employing a deflection sync separator 37 andproducing from the separated synchronizing impulse a horizontal sweepfrequency in horizontal sweep oscillator 39, and a vertical sweep signalin vertical sweep oscillator 41.

The appropriate sweep energy is applied to horizontal and verticaldefiection coils 43 and 45, also in the wellknown manner.

As has been outlined above, it is necessary, for accurate colorrepresentation, to employ careful synchronism in not only deflection,but in the rate or speed of dclection.

The sweep speed is controlled by obtaining from video amplifier 29 thesweep speed synchronizing impulses developed at the transmittingstation, as described above under Figure 1. This is accomplished by aclipping action in tube 47, which is appropriately biased to clip offonly a portion of the signal train developed in video amplifier 29. Inthe form of the invention shown, this sweep speed 'synchronizing pulseis developed in a white direction.

The sweep speed synchronizing pulse is then transmitted to a sweep speedcontrol, illustrated by dotted block 49, which operates to compare thesweep speed synchronizing pulse obtained from the transmitting systemwith the impulses developed at photocell 51, which is located behind anultraviolet filter 53, with respect to the `screen 3S of image.reproducing tube 33.

VAs the electron beam of kinescope 33 scans the target 35, an impulsewill be formed in tube 51 each time the scanning beam traverses theultraviolet filter section of target 35. Due to the limitation ofultraviolet filter 53, no impulses willbe formed in photoelectric cell51 while the scanning beam is scanning the red, blue or green filtersections of target 35.

Ifthe signal pulses obtained invphotocell 51 are compared with the sweepspeed synchronizing pulses obtained from the transmitter, it will beseen that an accurate sweep speed synchronization may be obtainedbetween the scanning beam of the transmitter tube 1 and the scanningbeam of the receiver tube 33. If, then, the order of the filter sectionsof the target 3 of Figure 1 and the target 35 of Figure 3 is arranged inthe same order, itwill be seen that the scanning beams of both thetransmitter tube 1 of Figure 1 and the receiving image produced ontarget 35 will correspond precisely, and the resultant image produced ontarget 35 will correspond to the image projected on the target 3 o-fFigure 1.

Although various arrangements are available for comparing thesynchronizing sweep speed impulse with the impulses derived fromphotocell 51, the circuit arrangement shown in Figure 3 is given by wayof example.

The sweep speed control circuit 49 involves a phase splitter amplifier55, which develops, together with diodes 57 and 59, a voltage which isdependent upon the synchronism of the sweep speed synchronizing signalderived from the transmitter and the impulses obtained from photocell51.

The operation of the circuit arrangement employed for sweep speedcontrol is well-known in the art and is illustrated in detail in theU.S. Patent No. 2,458,l56, issued to G..L. Fredendall.

It will be seen, after a brief examination of the circuit arrangementshown in block 49 of Figure 3, that the potential applied to the controlelectrode 61 of tube 63 is dependent upon whether or not the impulsesderived from photocell 51 lead or lag the impulses of the sweep speedsynchronizing impulses obtained from the transmitting system.

It therefore follows that the output signal obtained from tube 63 isdependent upon the sweepV speed of the electron beam developed inreceiving tube 33. y

The output energy from tube 63 may therefore be applied to horizontaldeflection coils 43 or it may be applied to an auxiliary horizontaldeilection coil not shown. It will be seen, therefore, that the outputenergy of tube 63 will control the sweep or traverse speed of thescanning beam of image reproducing tube 33 to synchronize accuratelywith the scanning speed of the electron beam developed in transmittertube 1 of Figure l.

This accurate control of sweep speed of the scanning beam of tube 33will result in accurate registration of corresponding color filtersections of both reproducing tube 33 and transmitter tube 1.

Having thus described the invention, what is claimed 1. In a colortelevision system of the type employing the transmission of differentselected component color image detail representative signals along eachscanning Iline by the modulation of a carrier with image detail signals,scanning synchronizing pulses and a periodic color phasing signal, thecombination of a modulated carrier signal receptor, signal separatorcircuits connected to `said receptor for developing separate imagedetail signals, scanning synchronizing pulses, and a periodic colorphas- Iing signal, a luminescent target, an electron scanning beam, beamdellecting means responsive to said synchronizing pulses to cause saidbeam to scan said target, means connected to said separator circuits andresponsive to said image detail signal for controlling the intensity ofsaid beam, and means for developing, in response to 'said periodic colorphasing signal, an auxiliary signal having a frequency which is amultiple of and greater than the frequency of said synchronizing pulses,and means responsive to said auxiliary signal for controlling colorphasing.

2. In color television transmitting apparatus, means scanning an imageline by line, means sequentially gen- `erating different selected colorimage detail representative color phasing signal between each of saidcolor sequences, the frequency of said color phasing signals being amultiple of and greater than the frequency of said line synchronizingpulses.

3. In a television transmitter a pickup tube having a target, saidtarget comprising a plurality of groups of parallel lines of chargeablematerial in sequence, means for charging one line in each group inaccordance with color information different from those of other lines ofsaid groups, a separating line of chargeable material between successiveones of said groups, means charging each of said separating lines to apredetermined value, means scanning said target and means generating asignal from each of said lines as said target is scanned, said signalsvarying in accordance with the charges appearing on said lines.

4. In color television receiving apparatus, means developing colorphasing pulses from received signals, the frequency of said pulses beinga multiple of and greater than the frequency of the line synchronizingsignals, a luminescent target, means scanning said target, meansincluding said scanning means locally generating color phasing pulses,means generating a control signal which varies in accordance with therelative phase of said developed and generated color phasing pulses, andmeans applying said control signal to the deflection system of saidscanning means.

5. In color television apparatus, a cathode ray tube having a targetconsisting of groups of parallel lines of material in sequence, eachline in a group being responsive to color information different fromthose of the other lines of each group, a separating line of materialbetween successive groups of lines, said separating lines beingresponsive to radiation energy outside of the visible spectrum, meanscausing the cathode ray beam of said tube to scan said target, meansgenerating a color phasing signal each time said beam crosses one ofsaid separating lines, means producing control signals from said colorphasing signals, and means to apply said control signals to the beamdeiiection system of said tube.

6. In color television apparatus a cathode ray tube having a targetconsisting of groups of parallel lines of chargeable screen material insequence, means for charging each line in a group in accordance withcolor information different from those of other lines of said group, aseparating line of chargeable screen material between said groups, meanscharging each of said separating lines to a predetermined value by meansof radiation energy outside of the visible spectrum, means causing thecathode ray beam of said tube to scan said target and means generating acolor phasing signal each time said beam crosses one of said separatinglines.

7. In a color television apparatus, a cathode ray tube having a targetconsisting of groups of parallel lines of screen material in sequence,each line in a group uorescing in a color different from those of otherlines in said group, separating lines of screen material between saidgroups, said separating lines liuorescing outside of the range ofvisible light, means causing the cathode ray beam of said tube to scansaid target, means generating a color phasing signal each time said beamcrosses one of said separating lines, meansproducing control signalsfrom said color phasing signals, and means to apply said control signalsto the beam deflection system of said tube.

8. A color television system employing a scanning beam for colorreproduction comprising in combination a source of image detail signals,scanning line synchronizing pulses and periodic color phasing signals,said color phasing signals being remotely and locally generated, meansfor developing from said color phasing signals an auxiliary signal, saidauxiliary signal having a frequency which is higher than the frequencyof said line synchronizing pulses, and means utilizing said developedauxiliary signal for phasing the color reproduction.

9. In color television receiving apparatus for receiving waves includingcontrol signals and signals representative respectively of differentcomponent colors of the transmitted image and succeeding each othersequentially in regularly recurring order, means for producing electronsin the form of at least one electron beam, ay screen comprising colorrepresentative phosphors effectively luminescent in different colorsunder impact of electrons, means for scanning the electrons over thescreen, said scanning means and said screen being constructed so thatdifferent color representative phosphors are impinged upon by theelectrons during each scanning line, and means responsive to the controlsignals in the received Waves for controlling the energization of thedifferent color representative phosphors along each separate scanmngline to make their energization accord withY the color representativesignals in the received Waves.

1G. In color television receiving apparatus for recelving Wavesincluding control signals and signals occupying respectively differentregularly recurring phases of a transmitting cycle and representativerespectively of different component colors of the transmitted image,means for producing electrons in the form of at least one electron beam,a screen comprising representative phosphors effectively luminescent indifferent colors When energized under impact of electrons, means forscanning the electrons over the screen, said scanning means and saidscreen being constructed so that different color representativephosphors are impinged upon by the electrons during each scanning line,and means responsive to the control signals in the received Waves forcontrolling the energization of the different color phosphors alongindividual scanning lines to make their energization accord with thedifferent phases ofthe color representative signals in the receivedwaves.

l1. In color television receiving apparatus for receiving wavesincluding field and line scanning synchronizing signals, additionalcontrol signals having a frequency much greater than and having apre-determined fixed ratio to the frequency ofthe line synchronizingsignals and signals occupying respectively different regularly recurringphases of a transmitting cycle and representative respectively ofdifferent component colors of the transmitted image, means for producingelectrons in the form of at least one electron beam, a screen comprisingcolor representative phosphors effectively luminescent in differentcolors when energized under impact of electrons, means under the`control of the field and line scanning synchronizing signals forscanning the electrons over the `screen, said scanning means and saidscreen being constructed so that different color representativephosphors are impinged upon by the electrons during each scanning line,and means responsive to said additional control signals in the receivedwaves for controlling the energization of the different colorrepresentative phosphors along each separate scanning line to make theirenergization accord with the different phases of the colorrepresentative signals in the received waves.

l2. In color television receiving apparatus for receiving wavesincluding control signals and signals representative respectively ofdifferent component colors of the transmitted image and succeeding eachother sequentially in regularly recurring order, means for producing anelectron beam, a screen containing color representative phosphorseffectively luminescent in different colors when energized under impactof the electron beam, means for scanning the electron beam over thescreen, said scanning means and said screen being constructed so thatdifferent color representative phosphors are impinged upon by the beamin regular order of recurrence during each scanning line, and meansresponsive to control signals in the received Waves for controlling theenergization of the different color phosphors along each separatescanning line to make their energization accord With tde sequence ofcolor representative signals inthe received waves.

13. In color television'receivingapparatus'for receiving waves includingcontrol signals and signals occupying respectively different regularlyrecurring phases of a transmitting cycle and representative respectivelyof different component colors of the transmitted image, means forproducing an electron beam, a screen containing color representativephosphors effectively luminescent in different colors when energizedunder impact of the electron beam, means for scanning the electron beamover the screen, said scanning means and said screen being constructedso that different color representative phosphors are impinged upon bythe beam in regular order of recurrence during each scanning line, andmeans responsive to control signals in the received waves forcontrolling the energization of the different color phosphors along eachseparate scanning line to make their energization accord with thedifferent phases of the color representative signals;

14. In color television receiving apparatus for receiving Wavesincluding control signals and signals representative respectively ofditerent component colors of the transmitted image and succeeding eachother sequentially in regularly recurring order, means for producing anelectron beam, a screen containing color representative phosphorseffectively luminescent in different colors when energized under impactof the electron beam, means for scanning the electron beam over thescreen, said scanning means and said screen being constructed so thatdifferent color representative phosphors are impinged upon by the beamin regular order of recurrence during each scanning line, and means forcontrolling the energization of the different color representativephosphors along each separate scanning line to make their energizationaccord with the sequence of color representative signals in the receivedwaves, said means including a source of local oscillations at thereceiver and connections for impressing on said source control signalsin the received waves.

15. In color television receiving apparatus for receiving wavesincluding control signals and signals occupying respectively differentregularly recurring phases of a transmitting cycle and representativerespectively of different component colors of the transmitted image,means for producing electrons in the form of at least one electron beam,a screen containing color representative phosphors effectivelyluminescent in `different colors when energized under impact ofelectrons, means for scanning the electrons over the screen, saidscanning means and said screen being constructed so that different colorrepresentative phosphors are impinged upon by the electrons during eachscanning line, and means'for controlling the energization of thedifferent color representative phosphors along each separate scanningline to make their energization accord with the different phases of thecolor representative signals in the received waves, said last-mentionedmeans including control circuits, a source of local oscillations at thereceiver, and connections for impressing on said control circuits saidlocal oscillations and control signals in the received Waves.

16. In color television receiving apparatus for receiving Wavesincluding control signals and signals representative respectively ofdifferent component colors of the transmitted image and succeeding eachother sequentially in regularly recurring order, means for producing anelectron beam, a screen containing substantially parallel colorrepresentative phosphor strips effectively luminescent in differentcolors when energized under impact of the electron beam, means forscanning the electron beam over scanning lines extending transversely ofthe strips, and means for controlling the energization of the differentcolor representative phosphor strips along each separate scanning lineto make their energization accord with the sequence of colorrepresentative signals in the received Waves, said means includingcontrol circuits, means for impressing on the control circuitsoscillatory energy produced by scanning action of the electron beam overthe phosphorstrips and -connections for .impressing on .said

agen-117 ctnitll `circuits control ,signals derived Vfrom the receivedvwaves including control signals and signals representative'respectively of different component colors of the transmitted image andsucceeding each other sequentially in regularly recurring order, meansfor producing an elec,- tron beam, a screen containing substantiallyparallel color representative phosphor strips effectively luminescent indifferent colors when energized under impact of, the electron beam,means for scanning the electron beam over scanning lines extendingtransversely of the strips, and means for controlling the energizationof the different color representative phosphor strips along eachseparate scanning line to make their energization accord with thesequence of color representative signals in the received waves, saidmeans including circuits for controlling the scanning speed of theelectron beam over individual scanning lines, means for impressing onsaid circuits oscillatory energy produced by scanning action of the`electron beam over the phosphor strips, and ,connections for impressingon said control circuits control signals derived from the receivedwaves.

18. In color television receiving apparatus for receiving wavesincluding control signalsand signals representative rmpectively ofdifferent component colors of the transmitted image and succeeding eachother sequentially in regularly recurring order, means for producing anelectron beam, -a screen containing substantially parallel colorrepresentative phosphor strips effectively luminescent in differentcolors when energized under impact of the electron beam, means formoving the electron beam over scanning lines extending transversely ofthe strips, and means for controlling the energization of the differentcolor representative phosphor strips along each separate scanning lineto make their energization accord with the sequence of colorrepresentative signals in the received Waves, said means includingcircuits for controlling the scanning speed of the electron beam overindividual scanning lines, means for producing oscillatory energyrelated in frequency to the line scanning of the electron `beam acrossthe screen, connections for impressing the oscillatory energy on thecircuits for controlling the scanning speed, and connections for alsoimpressing on said circuits control signals derived from the receivedwaves.

19. In a color television system, means for transmitting waves includingfield and line scanning synchronizing signals, additional controlsignals and image signals occupying respectively different regularlyrecurring phases of a transmitting cycle and representative respectivelyof different component colors of the transmitted image, and a receivercomprising means for producing electrons in the form of at least oneelectron beam, a screen comprising color representaive phosphorseffectively luminescent in different colors under impact of electrons,means under control of the transmitted field and line scanningsynchronizing signals for scanning the electrons over the screen, saidscanning means and said screen being constructed so that different colorrepresentative phosphors are impinged upon by the electrons during eachscanning line, and means responsive to the additional control signalsfor controlling the energization of the different color representativephosphors along each separate scanning line to make their energizationaccord with the different phases of the color representative signals inthe transmitted waves.

20. Apparatus according to claim 19 in which the additional controlsignals are of a frequency much greater than the line synchronizingsignals and have a fixed ratio to the frequency of the linesynchronizing signals.

21. Apparatus according to claim 20 in which the additional controlsignals are of substantially elemental frequency.

" 22.` In'a color television system, means for transmittingWaves-including field and line scanning synchronizing signals,additional control signals and image signals occupying respectivelydifferent regularly recurring phases of a transmitting cycle andrepresentative respectively of different component colors of thetransmitted image, Iand a receiver comprising means for producing anelectron beam, a screen comprising color representative phosphorseffectively luminescent in different colors under impact of electrons,means under control of the transmitted eld and line scanningsynchronizing signals for scanning the electron beam over the screen,said scanning means and said screen being constructed so` that differentcolor representative phosphors are impinged upon by the electron beamduring each scanning line, and means for controlling the energization ofthe different color representaive phosphors along individual scanninglines to make their energization accord with the different phases of thecolor representative signals in the transmitted waves, saidlast-mentioned means including control circuits, a source of localoscillations at the receiver, and connections for impressing on saidcontrol circuits said local oscillations and the transmitted additionalcontrol signals.

23. Apparatus according to claim 22 in which the additional controlsignals are of a frequency much greater than the line synchronizingsignals and have a fixed ratio to the frequency of the linesynchronizing signals.

24. Apparatus according to claim 23 in which the additional controlsignals are of substantially elemental frequency.

25. In a color television receiver, means for receiving a composite waveincluding line synchronizing signals defining line intervalstherebetween, image signals occupying respectively different regularlyrecurring phases of a transmitting cycle and representative respectivelyof different component colors of an image to be reproduced, andadditional control signals for frequency much greater than the linesynchronizing signals of fixed phase with respect to said regularlyrecurring phases of said image signals and having a fixed ratio to thefrequency of the line synchronizing signals, means for separating theadditional control signals from said composite wave, means sensitive tothe phases of said image signals coupled to said receiving means andincluding an image reproducing tube for producing an image in accordancewith information derived from said image signals, and phasing controlcircuits coupled to said separating means and responsive to saidadditional control signals for controlling the operation of said lastnamed means throughout each line interval.

26. Apparatus according to claim 25 in which the additional controlsignals are of substantially elemental frequency.

27. In combination: a source of an intelligence signal; a source of asecond signal synchronized with said intelligence signal and having aparameter indicative of the rate of change of intelligence in saidintelligence signal; a cathode ray tube including a source of anelectron beam, a beam intensity control electrode, a screen adapted forlight emission from a plurality of parallel strip-like regions, and aplurality of strip-like indexing elements placed near spaced ones ofsaid strip-like regions, each of said indexing elements being responsiveto beam impingement to produce an indexing signal indicative of suchimpingement, means for applying said intelligence signal to said beamintensity control electrode; means for deflecting said beam to cause itto scan said screen relatively slowly in a direction generally parallelto said strip-like regions yand to said indeXing elements and relativelyrapidly in a direction generally transverse to said strip-like regionsand to said indexing elements, said last-named means being responsive toa control signal to vary the rate of deflection of said beam in saiddirection transverse to said striplike regions and to saidindexingelements; means for deriving from said indexing signal a signalhaving a parameter indicative of the rate of traversal of said indexingelements by said beam; a signal comprising circuit-having a pair ofinput circuits and an output circuit, said input circuits being suppliedwith said last-named signal and with said second signal respectively andsaid signal comparing circuit being responsive toy relative changes insaid parameters of said supplied signals to produce in said outputcircuit a signal indicative of said relativechanges; and meansrforapplying said last-named signal to said deflection means as a controlsignal to alter the rate of deflection of said beam by said means.

28. In color television receiving apparatus including a source ofsignals occupying respectively different regularly recurring phases of atransmitting cycle and representative respectively of diierent componentcolors of the transmitted image and periodic color phasing signals,means for producing electrons in the form of at least one electron beam,an electron-responsive screen adapted to emit light of` dierent colorsfrom a plurality of strip-like regions arranged ink repeating groups,said screen having index material distributed thereacross foreffectively producing index signals in response to electron impingement,means for scanning Ithe electrons across said screen transversely ofsaid strip-like regions, said scanning means and said screen being con-:structed so that strip-like regions of different color emissioncharacteristics are successively impinged upon by the electrons duringeach scanning line, means for deriving from said index material anoscillating electrical index wave substantially throughout individualscanning lines, and means utilizing said received periodic color phasingsignals and responsive to said index wave for controlling the emissionof color light from said striplike regions along individual scanninglines to make such color light emission accord with the different phasesof the color representative signals from said source.

References Cited in the le of this patent UNITED STATES PATENTS2,415,059 Zworykin Jan. 28, 1947 2,490,812 Huffman` Dec. 13, 19492,621,244 Landon Dec. 9, 1952 2,621,245 Kell Dec. 9, 1952

